PTL 1 discloses a technique to reduce time required for resuming point to point protocol (PPP) connection by storing in a client an Internet protocol (IP) address when PPP connection is made last time.
NPL1 and NPL2 disclose a technique for making communication over network address translation (NAT).
NAT refers to a technique that enables a plurality of terminals in a local area network (LAN) to communicate with one global Internet protocol (IP) address. Specifically, NAT refers to a technique to represent different local addresses as different port numbers under an identical global address when a plurality of terminals within LAN inside home connect with a network outside LAN by a router performing identification or translation between IP addresses and port numbers.
Examples of the technique to make communication over NAT include a user datagram protocol (UDP) hole punching method and a method using universal plug and play (UPnP).
The UDP hole punching method is a method using simple traversal of user datagram protocol through NATs (STUN), etc. (for example, NPL1). Specifically, the UDP hole punching method is a method for connecting a server that provides services (for example, moving image server) to a router, and notifying a combination of an IP address and port number which can be accessed from outside and which are set in the router to a terminal that is a partner of peer to peer (P2P) connection (hereinafter referred to as “P2P partner terminal” or just “partner terminal”). The P2P partner terminal attempts access to the server by using the combination. This method is applicable to a router of an NAT method called Full-Cone NAT.
The method using UPnP is a method for a terminal within LAN (for example, moving image server) to set in the router a combination of an IP address and port number which are disclosed to outside, to notify set information to the P2P partner terminal, and then the P2P partner terminal attempts direct communication with the server by using the information. This method is applicable to a router in conformity with universal plug and play-Internet gateway device (UPnP-IGD) (for example, NPL2).
Both of the methods are methods for notifying the combination of the IP address and port number which are set in the router to the P2P partner terminal, and then the P2P partner terminal attempts direct communication with the server based on the information.